1. Field of the Invention
The present invention relates to an improved method for soldering a thermoelectric cooler between an electronic device and a heatsink to permit higher operating temperature of the assembly.
2. Description of Related Art
Thermoelectric coolers are used in the electronics industry to cool electronics devices. Thermoelectric coolers are assembled by soldering parts together using a first solder. Typically, the cooler is soldered to a heatsink and the electronic device is soldered to the cooler. Unless elaborate tooling is used, this is a two-step process. First, the thermoelectric cooler is soldered to the substrate or heatsink with a second solder which melts at a lower temperature than the melting temperature of the first solder used to assemble the cooler, which is about 138.degree. C. In one prior art approach, the second solder melts at 117.degree. C. The electronic device is then soldered to the thermoelectric cooler. To avoid having the thermoelectric cooler become detached from the heatsink while it is being soldered to the electronic device, a third solder is used having a melting point lower than the second solder, for example, about 93.degree. C. The operating and thermal cycle temperatures of the completed assembly are thus limited to below the melting temperature of the solder with the lowest liquidus. The use of the third solder having a melting point of 93.degree. C. becomes the limiting factor for the operating and thermal cycle temperatures of the assembled device.
Thus, a need exists to provide an improved method for soldering a thermoelectric cooler between an electronic device and a heatsink that avoids or minimizes the above mentioned disadvantages.